Add --parts command line option to LaTeX writer.

Add --parts command line argument.
This only effects LaTeX writer, and only for non-beamer output formats.
It changes the output levels so the top level is 'part', the next
'chapter' and then into sections.

MANUAL.txt

@@ -667,6 +667,11 @@ Options affecting specific writers
     option is implied.  If `beamer` is the output format, top-level
     headers will become `\part{..}`.
 
+`--parts`
+:   Treat top-level headers as parts in LaTeX output.  The second level
+    headers will be chapters, i.e. `--chapters` is implied.  This does not
+    effect the `beamer` output format.
+
 `-N`, `--number-sections`
 
 :   Number section headings in LaTeX, ConTeXt, HTML, or EPUB output.

pandoc.hs

@@ -184,6 +184,7 @@ data Opt = Opt
     , optHighlight         :: Bool    -- ^ Highlight source code
     , optHighlightStyle    :: Style   -- ^ Style to use for highlighted code
     , optChapters          :: Bool    -- ^ Use chapter for top-level sects
+    , optParts             :: Bool    -- ^ Use parts for top-level sects in latex
     , optHTMLMathMethod    :: HTMLMathMethod -- ^ Method to print HTML math
     , optReferenceODT      :: Maybe FilePath -- ^ Path of reference.odt
     , optReferenceDocx     :: Maybe FilePath -- ^ Path of reference.docx
@@ -249,6 +250,7 @@ defaultOpts = Opt
     , optHighlight             = True
     , optHighlightStyle        = pygments
     , optChapters              = False
+    , optParts                 = False
     , optHTMLMathMethod        = PlainMath
     , optReferenceODT          = Nothing
     , optReferenceDocx         = Nothing
@@ -609,6 +611,11 @@ options =
                   (\opt -> return opt { optChapters = True }))
                  "" -- "Use chapter for top-level sections in LaTeX, DocBook"
 
+    , Option "" ["parts"]
+                 (NoArg
+                  (\opt -> return opt { optParts = True }))
+                 "" -- "Use part for top-level sections in LaTeX"
+
     , Option "N" ["number-sections"]
                  (NoArg
                   (\opt -> return opt { optNumberSections = True }))
@@ -1124,6 +1131,7 @@ convertWithOpts opts args = do
               , optHighlightStyle        = highlightStyle
               , optChapters              = chapters
               , optHTMLMathMethod        = mathMethod'
+              , optParts                 = parts
               , optReferenceODT          = referenceODT
               , optReferenceDocx         = referenceDocx
               , optEpubStylesheet        = epubStylesheet
@@ -1387,6 +1395,7 @@ convertWithOpts opts args = do
                             writerHtml5            = html5,
                             writerHtmlQTags        = htmlQTags,
                             writerChapters         = chapters,
+                            writerParts            = parts,
                             writerListings         = listings,
                             writerBeamer           = False,
                             writerSlideLevel       = slideLevel,

src/Text/Pandoc/Options.hs

@@ -374,6 +374,7 @@ data WriterOptions = WriterOptions
   , writerBeamer           :: Bool       -- ^ Produce beamer LaTeX slide show
   , writerSlideLevel       :: Maybe Int  -- ^ Force header level of slides
   , writerChapters         :: Bool       -- ^ Use "chapter" for top-level sects
+  , writerParts            :: Bool       -- ^ Use "part" for top-level sects in LaTeX
   , writerListings         :: Bool       -- ^ Use listings package for code
   , writerHighlight        :: Bool       -- ^ Highlight source code
   , writerHighlightStyle   :: Style      -- ^ Style to use for highlighting
@@ -422,6 +423,7 @@ instance Default WriterOptions where
                       , writerBeamer           = False
                       , writerSlideLevel       = Nothing
                       , writerChapters         = False
+                      , writerParts            = False
                       , writerListings         = False
                       , writerHighlight        = False
                       , writerHighlightStyle   = pygments

src/Text/Pandoc/Writers/LaTeX.hs

@@ -750,18 +750,25 @@ sectionHeader unnumbered ident level lst = do
                          <> braces (text plain))
   book <- gets stBook
   opts <- gets stOptions
-  let level' = if book || writerChapters opts then level - 1 else level
+  let level' = case level of
+                 1 | writerParts opts            -> 0
+                   | writerBeamer opts           -> 0
+                   | book || writerChapters opts -> 1
+                   | otherwise                   -> 2
+                 _ | writerParts opts            -> level - 1
+                   | book || writerChapters opts -> level
+                   | otherwise                   -> level + 1
   let sectionType = case level' of
-                          0  | writerBeamer opts -> "part"
+                          0  -> "part"
-                             | otherwise -> "chapter"
+                          1  -> "chapter"
-                          1  -> "section"
+                          2  -> "section"
-                          2  -> "subsection"
+                          3  -> "subsection"
-                          3  -> "subsubsection"
+                          4  -> "subsubsection"
-                          4  -> "paragraph"
+                          5  -> "paragraph"
-                          5  -> "subparagraph"
+                          6  -> "subparagraph"
                           _  -> ""
   inQuote <- gets stInQuote
-  let prefix = if inQuote && level' >= 4
+  let prefix = if inQuote && level' >= 5
                   then text "\\mbox{}%"
                   -- needed for \paragraph, \subparagraph in quote environment
                   -- see http://tex.stackexchange.com/questions/169830/
@@ -770,7 +777,7 @@ sectionHeader unnumbered ident level lst = do
   let star = if unnumbered && level < 4 then text "*" else empty
   let stuffing = star <> optional <> contents
   stuffing' <- hypertarget ident $ text ('\\':sectionType) <> stuffing <> lab
-  return $ if level' > 5
+  return $ if level' > 6
               then txt
               else prefix $$ stuffing'
                    $$ if unnumbered